Battery and a battery encapsulation

ABSTRACT

A battery unit has a battery encapsulation formed by first and second encapsulation parts joined by a weld along a weld zone, with a battery contained in the battery encapsulation between the first and second encapsulation parts. Either the battery has a recess exstending along the weld zone, or overlaping edges of the first and second encapsulation parts are bent away from the battery to form a recess. The recess provides a heating insulating space that protects the battery from damage during welding along the weld zone.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery adapted to be located in abattery encapsulation, of the type having first and second encapsulationparts joined by a weld along a weld zone.

The invention also relates to such a battery encapsulation, and abattery unit having such a battery and such a battery encapsulation, thebattery being located in the encapsulation.

The invention also relates to an implantable medical device that hassuch a battery unit. Typically, the implantable medical device is aheart stimulating apparatus.

It should be noted that the invention particularly relates to a batteryunit, a battery and a battery encapsulation wherein the first and secondencapsulation parts are joined by welding with the battery beingdisposed in the encapsulation, generally in its operative position inthe encapsulation.

2. Description of the Prior Art

Since the invention is particularly applicable to batteries and batteryunits of implantable medical devices such as heart stimulatingapparatuses the background of the invention is described with referenceto such an application.

Batteries for implantable medical apparatuses are encapsulated inencapsulations made of a material compatible with the human body. Suchmaterials are metals such as stainless steel or titanium.

The encapsulation is constituted of two or more parts that have to bejoined with the battery positioned inside the encapsulation. Preferablythe encapsulation parts are joined by means of welding along overlappingedges thereof.

Welding will result in heat being generated in the very vicinity of thebattery itself. Normally, the battery is covered with an electricallyinsulating material, for example a polymer. The heat might negativelyaffect the battery or the insulating material covering it since thebattery is located close to the weld during the welding.

The conventional way to solve this problem is to use a support element,usually a polymer structure, which separates the battery from theencapsulation in the weld region. The support element may have a recessopposite the weld, thereby providing a clearance between itself and theweld zone or weld region. The support element thus prevents heattransfer through conduction directly to the support element, and thebattery. However, some space that could otherwise have been used asbattery space is lost in the encapsulation due to the presence of thesupport element. The support element also adds cost to the battery unit.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a battery unithaving a battery and a battery encapsulation of the type initiallydescribed that permits better use of space for the battery in theencapsulation than in known units, while at the same time permittingwelding of the encapsulation parts with the battery in place withoutdamaging the battery or any insulating material deposited thereonbecause of heat emanating from the weld.

It is a further object of the present invention to provide a batteryunit having a battery and a battery encapsulation of the type initiallydescribed that is advantageous to manufacture from an economical pointof view.

The above object is achieved by a battery of the type initially having arecess extending along a region corresponding to the weld zone, suchthat a heat insulating space is formed between the battery and theencapsulation along the weld zone.

The recess is located opposite to the weld zone, the depth and width ofthe recess being adapted such that heat emanating from the weld zoneduring welding does not have any detrimental effect on the battery.

According to a preferred embodiment, the battery is covered by an(electrically) insulating material, the depth and width of the recessbeing adapted such that heat emanating from the weld zone during weldingdoes not have any detrimental effect on the insulating material.

The object of the invention is also achieved by a battery encapsulationof the type initially described, along the weld zone, portions of thefirst and second encapsulation parts are bent away from a batterylocated in the encapsulation such that a heat insulating space is formedbetween the battery and the encapsulation along the weld zone.

The aforementioned portions are bent away to such an extent that heatemanating from the weld zone during welding does not have a detrimentaleffect on the battery or any electrically insulating material depositedon the battery.

The aforementioned portions extend along the complete length of the weldzone, or at least the or those parts of the weld zone that face thebattery.

In accordance with the above description, the invention also relates toa battery unit as initially described, having a battery according to theinvention.

The invention also relates to an implantable medical device having abattery unit as described above. According to one embodiment theimplantable medical device is a heart stimulating apparatus.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a conventional battery unit.

FIG. 2 is a cross sectional view of a part of the battery unit of FIG.1.

FIG. 3 is a cross sectional view of the same part of the battery unitshown in FIG. 1, but according to a first embodiment of the invention,

FIG. 4 is a cross sectional view of a part of the same part of thebattery unit shown in FIG. 1, but according to a second embodiment ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a battery unit 1, a part of which is shown in a crosssectional view in detail, according to prior art.

Here, the battery unit 1 is part of an implantable medical device, moreprecisely a heart stimulating apparatus such as a pacemaker to beimplanted in a mammal.

The battery unit 1 includes a battery 2 enclosed in an encapsulation 3having first and second parts 4,5 that are joined by a weld 13,preferably accomplished by laser welding. The battery 2 occupies a partof the interior of the encapsulation 3, while another part of theencapsulation interior is occupied by electronics (not shown) forcontrolling the operation of the device. On top of the battery unit 1and fixed thereto there is also provided a body 15, normally made of atransparent polymer, defining a connector body with connector elements(not shown) for the connection of leads to the battery 2.

The first and second parts 4,5 of the encapsulation 3 are joined alongopposite edges 6,7 thereof. The edges 6,7 overlap each other along theweld 13. One edge 6 is displaced inwardly by a spacing corresponding tothe thickness of the walls of the encapsulation parts 4. Thereby agenerally flat outer periphery of the small sides of the encapsulation 3is obtained, as well as an inner protuberance.

FIG. 2 shows a battery unit otherwise according to prior art, but whichhas a support element 8 for the battery 2 in the encapsulation 3. Thesupport element 8 forms a spacer between the battery 2 and theencapsulation all along the weld zone. In the support element 8 there isprovided a recess 9 opposite the weld zone 14 and extending over thelength of the weld zone 14 that it faces. The support element 8 usuallyis made of a polymer. The recess creates a space between heat affectedencapsulation 3 and battery 2 that prevents excessive heat transfer fromthe weld zone 14 to the battery 2 or any electrically insulating coating10 on the battery 2 during welding.

The battery is made of metal, such as stainless steel, and theinsulating coating material 10 is preferably a polymer such as siliconrubber, polypropylene (PP), polyfluorethylene or any other suitableelectrically insulating material.

The encapsulation 3 preferably is made of a material accepted by thehuman body, such as titanium or stainless steel.

As an alternative to the battery unit 1 according to FIG. 2 it wouldalso be possible to have a battery unit without any support element.Such a battery unit is shown in FIG. 3 but without further steps wouldhave the disadvantage of excessive heat being transferred from the weldzone to the battery 2 during welding. The transferred heat may damagethe battery 2 or any coating of electrically insulating material 10provided thereon.

FIG. 3 shows a first embodiment of the inventive battery unit 1. Here,the battery 2 has a recess 11 extending along a region corresponding tothe weld zone 14 adjacent the battery 2, such that a heat insulatingspace 12 is formed between the battery 2 and the encapsulation 3 alongthis part of the weld zone 14. Thereby excessive heat transfer isprevented from damaging the battery 2 or its insulation material 10. Itis evident that only the part of the battery 2 that is facing the weldzone 14 need be provided with the recess 11. Normally, at least threeout of the four of a generally flat, rectangular battery's small sidesneed to be provided with this recess. A recess is not necessary in thefourth small side of the battery that faces the electronics, ifpreferred from a production cost saving point of view.

The length of the recess 11 corresponds to the length of the part of theweld 13 that it faces. The depth of the recess 11 is such that aninsulating space of 0.05 to 0.30 mm is obtained between the innerperiphery of the weld zone 14 of the encapsulation 3 and the battery 2.One of the overlapping edges 6,7 is displaced inwards with a distancecorresponding to the thickness of the encapsulation wall in order toprovide a generally flat outer periphery along the joint between theencapsulation parts 4,5. Thereby, the actual depth of the recess in thisembodiment is equal to the encapsulation wall thickness plus 0.05–0.30mm.

The width of the recess is at least 0.2 to 0.6 mm larger than the widthof the weld zone 14. Preferably, the width of the recess is 0.2–0.6 mmlarger than the width of the overlapping edge 6 that protrudes inwardstowards the battery 2. Thereby a preferred lateral spacing of 0.1 to 0.3mm is created between battery 2 and encapsulation 3 on each side of theoverlapping parts of the edges 6,7 or, more precisely, the protuberanceformed by the inner edge 6.

FIG. 4 shows a second embodiment of the inventive battery unit 1. Here,the recess in the battery 2 has been replaced by a correspondingconvexity of the edges 6,7 of the encapsulation. That is, the edges 6,7are pre-bent before welding such that, with a conventional flat battery2 inside the encapsulation 3, there will be an insulating space 12between the battery 2 and inner periphery of the encapsulation along theweld zone 14.

The edges 6,7 are bent away from the interior of the encapsulation tosuch an extent that the heat insulating space thereby obtained has awidth and a depth corresponding to the one mentioned above for the firstembodiment.

It should be understood that the above embodiments have been disclosedonly as an example, and that the invention is not restricted to theseembodiments. A number of alternative embodiments will be apparent tothose skilled in the art without departing from the inventive concept.

For example, in the first embodiment, the small sides of theencapsulation 3 that face the battery 2 protrude inwardly along theoverlapping portions 6,7, whereby the heat insulating space betweenbattery and enclosure is obtained thanks only to the provision of therecess in the battery. In the second embodiment, the heat insulatingspace is provided through the provision of the bent encapsulation edgeportions 6,7, the small sides of the battery 2 directed thereto beinggenerally flat (without recess). It should be understood that acombination of the first and second embodiments of the invention asdescribed above is within the scope of the invention as long as theinsulating space thereby created corresponds to that defined above foreach individual embodiment.

The term “weld zone” as used herein refers to at least a region of theencapsulation located adjacent to the weld, the structure of which isvisibly or at least physically altered due to the heat it is exposed toduring welding.

Although modifications and changes may be suggested by those skilled inthe art, it is the invention of the inventor to embody within the patentwarranted heron all changes and modifications as reasonably and properlycome within the scope of his contribution to the art.

1. A battery adapted to be contained in a battery encapsulation having a seam closed by a weld along a weld zone, said battery comprising: a battery body adapted to be contained in said battery encapsulation; and said battery body having a recess extending along a region of said battery corresponding to said weld zone, said recess forming a heat insulating space between said battery body and said encapsulation along said weld zone.
 2. A battery as claimed in claim 1 wherein said recess is disposed opposite said weld zone when said battery body is disposed in said battery encapsulation, and wherein said recess has a depth and a width selected to prevent heat emanating from said weld zone during welding of said seam from having a detrimental effect on said battery body.
 3. A battery as claimed in claim 1 comprising insulating material covering said battery body, and wherein said recess covered by said insulating material has a depth and a width selected for preventing heat emanating from said weld zone during welding of said seam from having a detrimental effect on said insulating material.
 4. A battery as claimed in claim 1 wherein said battery encapsulation has parts in said weld zone facing said battery body, said parts having a length, and wherein said recess has a length corresponding to said length of said parts.
 5. A battery as claimed in claim 1 wherein said battery encapsulation has an interior periphery along said weld zone, and wherein said recess has a depth for maintaining a spacing between said battery body and said inner periphery in a range between 0.05 and 0.30 mm.
 6. A battery as claimed in claim 1 wherein said weld zone has a width, and wherein said recess has a width that is larger than the width of said weld zone by an amount in a range between 0.2 and 0.6 mm.
 7. A battery as claimed in claim 1 wherein said battery encapsulation has overlapping edges forming said seam that are welded together by said weld in said weld zone, said overlapping edges having a width, and wherein said recess has a width that is larger than said width of said overlapping edges by an amount in a range between 0.2 and 0.6 mm for producing a lateral spacing in a range between 0.1 and 0.3 mm between said battery body and said battery encapsulation on each side of said overlapping edges.
 8. A battery encapsulation adapted to contain a battery therein, said battery encapsulation comprising: a first encapsulation part and a second encapsulation part; said first and second encapsulation parts being joined at a seam by a weld along a weld zone; and along said weld zone, each of said first and second encapsulation parts having a portion bent away from a battery contained in said first and second encapsulation parts, forming a heat insulating space between the battery and said first and second encapsulation parts along said weld zone.
 9. A battery encapsulation as claimed in claim 8 wherein said portions of said first and second encapsulation parts are bent away for producing said heat insulating space with a size for preventing heat emanating from said weld zone during welding from having a detrimental effect on the battery.
 10. A battery encapsulation as claimed in claim 8 wherein said battery is covered by an insulating material and wherein said portions of said first and second encapsulation parts are bent away for forming said heat insulating space with a size for preventing heat emanating from said weld zone during welding from having a detrimental effect on said insulating material.
 11. A battery encapsulation as claimed in claim 8 wherein said weld zone has a weld zone portion facing said battery, and wherein said portions of said first and second encapsulation parts extend along said weld zone portion.
 12. A battery encapsulation as claimed in claim 8 wherein said portions of said first and second encapsulation parts are bent away to form said heat insulating space with a depth in a range between 0.05 and 0.30 mm.
 13. A battery encapsulation as claimed in claim 8 wherein said weld zone has a width, and wherein said portions of said first and second encapsulation parts are bent away for forming said heat insulating space with a width that is larger than said width of said weld zone by an amount in a range between 0.2 and 0.6 mm.
 14. A battery unit comprising: a battery; a battery encapsulation comprising a first encapsulation part and a second encapsulation part joined at a seam by a weld along a weld zone, said battery being disposed in said battery encapsulation between said first and second encapsulation parts; and said battery having a recess extending along said weld zone and forming a heat insulating space between said battery and said battery encapsulation along said weld zone.
 15. A battery unit as claimed in claim 14 wherein said recess is disposed opposite said weld zone, and wherein said recess has a depth and a width selected for preventing heat emanating from said weld zone during welding from having a detrimental effect on said battery.
 16. A battery unit as claimed in claim 14 wherein said battery has a covering composed of an insulating material, and wherein said recess has a depth and width selected for preventing heat emanating from said weld zone during welding from having a detrimental effect on said insulating material.
 17. A battery unit as claimed in claim 14 wherein said weld zone has a weld zone region facing said battery, said weld zone region having a length, and wherein said recess has a length corresponding to said length of said weld zone region.
 18. A battery unit as claimed in claim 14 wherein said battery encapsulation has an interior periphery along said weld zone, and wherein said recess has a depth selected for producing a spacing between said interior periphery and said battery in a range between 0.05 and 0.30 mm.
 19. A battery unit as claimed in claim 14 wherein said weld zone has a width, and wherein said recess has a width that is larger than said width of said weld zone by an amount in a range between 0.2 and 0.6 mm.
 20. A battery unit as claimed in claim 14 wherein said first and second encapsulation parts have respective overlapping edges forming said seam that are welded together by said weld in said weld zone, said overlapping edges having a width, and said recess having a width that is larger than said width of said overlapping edges by an amount in a range between 0.2 and 0.6 mm, for producing a lateral spacing in a range between 0.1 and 0.3 mm between said battery and said battery encapsulation on each side of said overlapping edges. 